Coal mines make expensive batteries

Tuesday, June 6th, 2017

The growth of not-so-on-demand renewable power sources has people looking at converting coal mines into pumped-hydro energy-storage systemes:

Compared with other types of energy storage, the underground pump concept is expensive but designed to last longer than a chemical battery.

The cost of the German system is about €2,750 ($3,075) per kilowatt-hour. New Jersey-based Eos Energy Storage, a cutting-edge battery company, offers a storage system powered by zinc-hybrid batteries for $168 a kilowatt-hour that can last around 20 years, according to the company’s director of business development, Charles Russell.

“The advantage of pumped hydro is that it’s high capex, but it’s there for 100 years,” said Gerard Reid, a founding partner at Alexa Capital, a London-based corporate finance firm specializing in energy technology and infrastructure.

The engineer’s report described the pump as “long-lasting and virtually maintenance free.”

But there is another problem affecting all types of power-storage systems. Even if an investor fronted the money to build the pump, the low price of electricity on both sides of the Atlantic would make it difficult to turn a profit. For the pump to make money, it needs wide spreads in the wholesale power market, so it can buy power when prices are low and sell when prices are high.

Right now, wholesale electricity is cheap pretty much all the time.


  1. Alrenous says:

    So the mine battery only needs to last for four times its rated duration, assuming you’re fine with just breaking even.

    I’m sure it’s fantastic graft though. Truly superb.

  2. Handle says:

    If you think about it, the combination of (working) coal mine, transportation system, and power plant is a kind of “battery”, though one the wattage for which is hard and slow to “throttle”. Still beats solar and wind, which can’t be throttled at all.

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